FAQ – Nature in the Audomarois marsh: fauna and flora
Answers to your questions about the plants and animals of the marsh around St Omer
Welcome to our FAQ dedicated to discovering and understanding the natural wealth of the Marais Audomarois. This exceptional site, located in the heart of a preserved environment, is home to remarkable biodiversity that deserves our full attention. Here, we invite you to explore in depth the variety of fauna and flora that make up this unique ecosystem.
The FAQ covers the many migratory and resident birds that populate these places, the fish that thrive in the calm waters, as well as the nocturnal bats that ensure the balance of the environment. We will also address the presence of invasive species, the management of which is crucial to preserve local biodiversity.
On the plant side, the Marais Audomarois is distinguished by its century-old trees, aquatic plants and rare species, real treasures to be protected. Through a set of detailed questions and answers, we highlight the complex interactions between these elements and the conservation initiatives underway.
The Audomarois marsh is home to a great diversity of birds, with more than 200 species recorded. Here are the main birds that can be observed there:
Grey Heron: Easily recognizable, it measures up to 1 meter in height with a wingspan of almost 2 meters.
Kingfisher: Recognizable by its metallic blue plumage and orange throat.
Coot: Very common in the marsh, it moves in groups. It is recognized by its black body and its white frontal bar extending its beak.
Moorhen: Recognizable by its dark plumage, its red beak with a yellow tip and its long green-yellow legs.
Common Tern: Observed hunting fish on the surface during the breeding season. It is recognized by its red and black beak and its white-grey plumage.
Common snipe: Present mainly during migration and wintering periods.
Little Bittern: An emblematic species of the marsh, this little heron is difficult to observe due to its discreet behavior.
Mallard Duck: A common wild duck in the marsh.
Marsh harrier: Frequents the reed beds of the marsh.
Reed Bunting: Also present in reed beds.
Mute swan: very common in this environment.
Stork: present since 2014
Little Grebes and Great Crested Grebes: two outstanding fishermen!
Other notable species include the little egret, the bittern, and various species of ducks such as the green-winged teal and the northern shoveler.
Find our full article here on the birds of the marsh.
Several rare birds deserve special attention for their preservation in the Audomarois marsh:
The little bittern: Considered the emblematic species of the site, this small heron hides in the reeds to hunt. It goes back up every spring towards France, and in particular to the Audomarois marsh, which is home to 10% of the French bittern population. The colonies are established in the Romelaere reserve.
The bittern: Mentioned as an important marsh species.
The luscinioid grasshopper: A migratory bird that builds its nest among the stems of reeds.
The aquatic warbler: The Audomarois marsh is a site of national importance for the migration of this species.
marsh harrier : Frequents the reed beds of the marsh.
The Bluethroat : Cited among the remarkable species of the site.
The marsh mystic : Although it is a bat and not a bird, it is mentioned as the rarest species in France present in the marsh.
These species are particularly vulnerable to threats to the marsh, such as drying out, eutrophication and discharges from human activities. Preserving their habitats, including reed beds and wetlands, is crucial for their survival in this unique ecosystem.
Here is the list of fish that can be commonly found in the Audomarois marsh:
- Pike (Esox lucius)
- pole
- Sandre
- Common carp (Cyprinus carpio)
- Roach
- rudd
- Common bream (Abramis brama)
- Border bream (Blicca bjoerkna)
- Tench
- Stud
- Bleak
- European eel (Anguilla anguilla)
- Cowherd (Rhodeus amarus)
- Common crucian carp (Carassius carassius)
- White fish (various species)
According to inventories, the Audomarois marsh is home to a total of 26 species of fish. However, the sources do not provide an exhaustive list of the 26 species.
It is important to note that some species, such as pike, are listed on the IUCN Red List of freshwater fish in France, which highlights the importance of preserving this habitat for fish biodiversity.
Find our article on the fish from the Audomarois marsh.
The eel is indeed endangered in the Audomarois marsh. This species, once abundant in the region, is experiencing a significant decline and is now considered highly threatened.
The European eel, which was present in large numbers in the Audomarois marsh until the 1980s and 1990s, is now classified as an endangered species by the IUCN (International Union for Conservation of Nature) Red List. This alarming situation has led to the implementation of various conservation and management measures.
Several factors contribute to the disappearance of the eel in the Audomarois marsh:
- Water pollution
- Pumping and drainage facilities, locks and other dams limiting migration to the Sargasso Sea, the breeding ground for eels
- Parasitism
- Overfishing of fry (elvers) in estuaries.
Faced with this critical situation, various initiatives have been put in place:
- Conservation measures have been put in place, particularly within the framework of the National Eel Management Plan.
- Efforts are being made to improve the free movement of fish, in accordance with Article L214-17 of the Environmental Code.
The preservation of the eel has become a major issue for the biodiversity of the Audomarois marsh, and actions are being taken to restore and preserve its habitats, as well as to protect it during dredging and mowing work.
Here are the main invasive animal species present in the Audomarois marsh:
Muskrat: Mentioned as one of the most common invasive species in the marsh. Note that we do not find the nutria, its cousin, in our environment.
Exotic fish: 6 of the 29 species of fish present in the marsh are considered exogenous.
American crayfish.
The Audomarois marsh is home to an exceptionally rich and diverse flora:
More than 400 species of flowering plants have been listed. This represents a third of the French aquatic flora and 50% of the regional aquatic flora. Nearly 300 varieties of plants, including 249 species of higher plants, have also been identified in the regional nature reserve.
Among the remarkable and emblematic species, we note the presence of purple loosestrife and the white water lily and the yellow water lily.
Unfortunately, the marsh is also faced with invasive species:
- Creeping water hyacinth: exotic plant native to South America, very invasive.
- Brazilian watermilfoil: another invasive plant native to Latin America.
The floral richness of the Audomarois marsh contributes to its status as a UNESCO biosphere reserve and underlines the importance of its preservation, especially since 53% of the species present are endangered according to the IUCN.
Although not a tree species in the traditional sense, the pollarded willow (or "cat's head") is an emblematic figure in the landscape of the Audomarois marsh. These are willows that are regularly pollarded, which gives them a characteristic "head" shape. These trees have been pruned in this way for centuries for several reasons:
- Wickerwork Production: The thin, flexible branches of the pollard willow are ideal for making baskets, fences, and other wicker objects.
- Bank stabilization: Willow roots help maintain the banks of waterways (canals) and prevent erosion.
- Maintaining an open landscape: Regularly topping willows helps control their growth and prevent them from obstructing waterways or shading out vegetable crops.
- Wildlife Habitat: The cavities in the trunks of pollarded willows provide shelter and nesting grounds for many animals, including birds, insects and small mammals.
